Method and plant for processing biological substrate

Abstract

The invention relates to a method for processing biological substrate, comprising the steps of: a) introducing the biological substrate into an apparatus for dry fermentation, b) carrying out dry fermentation to recover methane, forming fermentation residue, c) transferring the fermentation residue obtained in step b) to an apparatus for solid-liquid separation, d) carrying out solid-liquid separation of the fermentation residue, forming a fermentation residue solid phase and a fermentation residue raw liquid phase, e) transferring the fermentation residue raw liquid phase obtained in step d) to an apparatus for separating solids, f) carrying out separation of solids from the fermentation residue raw liquid phase, recovering a fermentation residue liquid phase, g) introducing the fermentation residue liquid phase obtained in step f) into an apparatus for wet fermentation, h) carrying out wet fermentation to recover methane, forming liquid fermentation residue, i) returning at least some of the liquid fermentation residue formed in step h) as inoculum to the apparatus for dry fermentation.

1 . A method for processing biological substrate comprising the following steps:
 a) introducing the biological substrate into a dry fermentation apparatus,   b) carrying out dry fermentation to obtain methane with formation of a fermentation residue,   c) transferring the fermentation residue obtained in step b) to an apparatus for solid/liquid separation,   d) carrying out a solid/liquid separation of the fermentation residue to form a fermentation residue solid phase and a fermentation residue liquid crude phase,   e) transferring the fermentation residue liquid crude phase obtained in step d) to an apparatus for separating solids,   f) carrying out a separation of solids from the fermentation residue liquid crude phase to obtain a fermentation residue liquid phase,   g) introducing the fermentation residue liquid phase obtained in step f) into an apparatus for wet fermentation,   h) carrying out a wet fermentation to obtain methane with formation of a liquid fermentation residue,   i) returning at least part of the liquid fermentation residue formed in step h) as inoculum to the dry fermentation apparatus.   
     
     
         2 . The method according to  claim 1 , wherein, as step i), the step
 i) returning a first portion of the liquid fermentation residue formed in step h) as inoculum to the dry fermentation apparatus and transferring a second portion of the liquid fermentation residue formed in step h) to an apparatus for hygienisation is carried out, and, after step i), the step   j) hygienising the second portion of the liquid fermentation residue formed in step h) with formation of an agriculturally usable biological material,   is carried out.   
     
     
         3 . The method according to  claim 2 , wherein in step j) the hygienisation takes place at a temperature between 65° C. and 75° C., preferably at a temperature of 70° C. 
     
     
         4 . The method according to  claim 2 , wherein in step j) the hygienisation takes place with a residence time of the liquid fermentation residue of between 45 min and 75 min, preferably with a residence time of 60 min. 
     
     
         5 . The method according to  claim 1 , wherein, after step d), the steps
 d 0 ) transferring the fermentation residue solid phase obtained in step d) to an apparatus for composting biological material   and   d 1 ) carrying out composting of the fermentation residue solid phase obtained in step d) in the apparatus for composting biological material are carried out.   
     
     
         6 . The method according to  claim 5 , wherein in step d 1 ) the composting is carried out without admixing additional, untreated biological substrate. 
     
     
         7 . The method according to  claim 1 , wherein the separation of solids from the fermentation residue liquid crude phase to obtain a fermentation residue liquid phase in step f) is carried out by density separation, in particular by density separation using a press, a grit separator, a decanter, a sieve or a settling tank. 
     
     
         8 . The method according to  claim 1 , wherein the fermentation residue liquid phase introduced into the apparatus for wet fermentation in step g) has a dry matter content of less than 15%. 
     
     
         9 . The method according to  claim 1 , wherein the wet fermentation carried out in step h) is carried out with admixture of additional biological substrate. 
     
     
         10 . The method according to  claim 9 , wherein the additional biological substrate admixed in step h) is manure, catering waste, food scraps, market waste or mixtures of these substrates. 
     
     
         11 . The method according to  claim 1 , wherein in step b) the dry fermentation to obtain methane is carried out with a residence time of the biological substrate in the dry fermentation apparatus of 10 to 19 days, preferably with a residence time of 12 to 17 days. 
     
     
         12 . The method according to  claim 1 , wherein the solids separated from the fermentation residue liquid crude phase in step f) are stones, sand, glass and/or pieces of metal. 
     
     
         13 . The method according to  claim 1 , wherein the biological substrate introduced into the dry fermentation apparatus in step a) has a dry matter content of between 15% and 60%, preferably between 25% and 50%. 
     
     
         14 . A plant for processing biological substrate comprising
 at least one dry fermentation apparatus,   at least one apparatus for solid/liquid separation,   at least one apparatus for separating solids,   at least one apparatus for wet fermentation, and   at least one apparatus for returning liquid fermentation residue as inoculum to the dry fermentation apparatus.   
     
     
         15 . The plant according to  claim 14 , wherein an apparatus for the hygienisation of liquid fermentation residue is additionally provided. 
     
     
         16 . The plant according to  claim 14 , wherein an apparatus for composting biological material is additionally provided. 
     
     
         17 . The plant according to  claim 14 , wherein the dry fermentation apparatus is a plug-flow fermenter. 
     
     
         18 . The plant according to  claim 14 , wherein the solid/liquid separation apparatus is a press-screw separator. 
     
     
         19 . The plant according to  claim 14 , wherein the apparatus for separating solids is a press, a grit separator, a decanter, a sieve or a settling tank. 
     
     
         20 . The plant according to  claim 16 , wherein the apparatus for composting biological material is a post-rotting apparatus.